// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2022 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_NODE_UTXO_SNAPSHOT_H
#define BITCOIN_NODE_UTXO_SNAPSHOT_H

#include <fs.h>
#include <kernel/cs_main.h>
#include <serialize.h>
#include <sync.h>
#include <uint256.h>

#include <cstdint>
#include <optional>
#include <string_view>

class Chainstate;

namespace node {
//! Metadata describing a serialized version of a UTXO set from which an
//! assumeutxo Chainstate can be constructed.
class SnapshotMetadata
{
public:
    //! The hash of the block that reflects the tip of the chain for the
    //! UTXO set contained in this snapshot.
    uint256 m_base_blockhash;

    //! The number of coins in the UTXO set contained in this snapshot. Used
    //! during snapshot load to estimate progress of UTXO set reconstruction.
    uint64_t m_coins_count = 0;

    SnapshotMetadata() { }
    SnapshotMetadata(
        const uint256& base_blockhash,
        uint64_t coins_count,
        unsigned int nchaintx) :
            m_base_blockhash(base_blockhash),
            m_coins_count(coins_count) { }

    SERIALIZE_METHODS(SnapshotMetadata, obj) { READWRITE(obj.m_base_blockhash, obj.m_coins_count); }
};

//! The file in the snapshot chainstate dir which stores the base blockhash. This is
//! needed to reconstruct snapshot chainstates on init.
//!
//! Because we only allow loading a single snapshot at a time, there will only be one
//! chainstate directory with this filename present within it.
const fs::path SNAPSHOT_BLOCKHASH_FILENAME{"base_blockhash"};

//! Write out the blockhash of the snapshot base block that was used to construct
//! this chainstate. This value is read in during subsequent initializations and
//! used to reconstruct snapshot-based chainstates.
bool WriteSnapshotBaseBlockhash(Chainstate& snapshot_chainstate)
    EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

//! Read the blockhash of the snapshot base block that was used to construct the
//! chainstate.
std::optional<uint256> ReadSnapshotBaseBlockhash(fs::path chaindir)
    EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

//! Suffix appended to the chainstate (leveldb) dir when created based upon
//! a snapshot.
constexpr std::string_view SNAPSHOT_CHAINSTATE_SUFFIX = "_snapshot";


//! Return a path to the snapshot-based chainstate dir, if one exists.
std::optional<fs::path> FindSnapshotChainstateDir();

} // namespace node

#endif // BITCOIN_NODE_UTXO_SNAPSHOT_H
